1. Field of Invention
The present invention relates to a wafer-cleaning device. More particularly, the present invention relates to a device for cleaning the surface of a silicon wafer after chemical-mechanical polishing (CMP).
2. Description of Related Art
In the process of manufacturing semiconductor devices, silicon wafers are frequently planarized after a particular treatment such as sputtering or deposition. At present, the chemical-mechanical polishing (CMP) method has become one of the most frequently used manufacturing techniques for the global planarization of silicon wafers. However, whenever a silicon wafer is polished, a large quantity of small chips or particles is also produced. Therefore, a post CMP cleaning operation is often required to clear away these unwanted particles from the wafer surface and edge.
A conventional post CMP cleaning operation involves the use of a brush roller or a pen brush. FIGS. 1A and 1B show the respective schematic top and front view of a conventional brush roller type of wafer cleaning device. The top surface of a wafer 10 is cleaned using a brush roller 12. During a wafer cleaning operation, the wafer 10 rotates in the direction A while the brush roller 12 rotates in the direction B (as shown in FIG. 1B). Through the simultaneous movement of the wafer 10 and the brush roller 12, the entire surface of the wafer 10 is ultimately cleaned.
FIGS. 2A and 2B show the respective schematic top and front view of a conventional pen brush type of cleaning device. The top surface of a wafer 10 is cleaned using a pen brush 14. During a wafer cleaning operation, the wafer 10 rotates in the direction A while the pen brush moves horizontally across the wafer in the direction 13 (as shown in FIG. 2B). Through the simultaneous movement of the wafer 10 and the pen brush 14, the entire surface of the wafer 10 is ultimately cleaned.
In general, after the loose chips or particles are scooped up by a brush roller 12 or a pen brush 14, these chips or particles have to be carried away by flowing liquid or chemical agent. Yet, no matter whether a brush roller or a pen brush is used, it is difficult to provide a wafer whose surface maintains a uniform alkalinity/acidity or pH value by conventional techniques. This is because these types of cleaning methods can only provide cleaning in a localized region at any one moment.
In addition, the scooped-up chips or particles will eventually fall back onto the wafer surface due to gravity. As these particles hit the wafer surface, the surface may be scratched or damaged again.
Hence, a brush roller or a pen brush can at best achieve a localized silicon particle removal. For example, a brush roller type can remove a narrow band of particles from the wafer surface at one time, and a pen brush can remove the particles surrounding the pen brush at any one time. In fact, both types of cleaning can be considered cleaning processes achieved through the piece-wise addition of a large number of localized cleaning operations.
Furthermore, since the aforementioned methods clean only a limited region of the silicon wafer at any one time, a longer period is required to clean up the entire wafer surface. Consequently, time is wasted in the cleaning operation.
In light of the foregoing, there is a need to provide a global wafer-cleaning device.